In recent years, as electrophotographic photoreceptors, organic photoreceptors comprising organic photoconductive materials have been widely employed. Organic photoreceptors are superior to other photoreceptors in such a manner that it is easier to develop materials in response to various types of exposure light sources ranging from visible light to infrared light; it is possible to select materials which result in no environmental pollution; the production cost is lower; and the like. However, the organic photoreceptors have problems in which their mechanical strength is low, and during copying a large volume, as well as during normal printing, the photoreceptor surface results in degradation as well as abrasion.
The aforementioned organic photoreceptor exhibits a large frictional resistance against a cleaning blade employed to remove residual toner. As a result, the surface of said photoreceptor is subjected to wear as well as abrasion.
On the other hand, in order to improve the mechanical strength of the electrographic photoreceptor, heretofore, various matters have been investigated.
Regarding mechanical durability, it is reported that by employing bisphenol Z type polycarbonates as a binder, the surface frictional properties as well as toner filming properties are improved. Further, Japanese Patent Publication Open to Public Inspection No. 6-118681 discloses that colloidal silica containing hardenable silicone resin is employed as the surface layer of a photoreceptor.
However, the photoreceptor, in which bisphenol type polycarbonate binder is employed, exhibits neither sufficient wear resistance properties nor sufficient durability. On the other hand, wear resistant properties of the surface layer comprised of colloidal silica containing hardenable resin are improved. However, during repeated use, electrophotographic properties are not sufficient, and background staining as well as image blurring result. Thus, sufficient durability is not obtained.
As one of several methods to overcome such problems, an attempt has been carried out in which fatty acid metal salts are incorporated into the developer material, and during development, a thin layer of said fatty acid metal salt is formed on the photoreceptor surface to decrease the frictional resistance against said cleaning blade. However, when this method is employed, the surface of a conventional photoreceptor suffers from a large decrease in layer thickness due to wear, and further, the decrease in the frictional resistance due to the formation of the thin layer of fatty acid salt exhibits only temporary effects.
Further, as a method to overcome the aforementioned problems, the inventors of the present invention proposed a charge transferable polysiloxane hardenable resin layer as the surface layer of a photoreceptor (Japanese Patent Application No. 11-70308). The wear resistance as well as ambient resistance (variations of electrostatic properties with respect to temperature and humidity) is improved. However, when structure units having a charge transferability were built in, it was found that problems occurred in which the wear of the edge of a cleaning blade was greater, being different from conventional organic photoreceptors, especially at high temperature and high humidity ambience (hereinafter referred to as HH ambience) and cleaning properties at the HH ambience were degraded.